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The engine is one of the essential components of cars. If there is an issue with the engine, it can be one of the most expensive things to replace. When it starts to react differently to everyday driving, you should be alert to fix the issue as soon as possible. Two of the most concerning problems are whether the engine overheats or runs very high RPM without using the accelerator.

What is RPM?

Tachometer with gauges
Tachometer | Getty Images

You may have noticed the other big gauge in your car beside the speedometer. The gauge is called the tachometer and measures your RPM. Revolutions Per Minute is how fast the engine operates the normal combustion cycle. It measures how many times the crankshaft completes one rotation every minute. More RPM does not always mean faster movement. Every car has a specific RPM where peak horsepower comes in. On your tachometer, a red section indicates the limit of the engine rotation. If you notice the tachometer fluctuating and the car shaking or increasing on its own, your engine may have an issue.

What causes RPM to increase so much?

Mercedes Engine in factory
Mercedes Engine with Automatic Transmission | Getty Images

There are a large number of ways to treat this problem. Diagnosing the issue is the first step, and there are many ways to do this. Common symptoms and causes give you an excellent place to start narrowing down the problem. According to J.D. Power, there are six common issues for high RPM. First, a bad idle control valve on the throttle body of fuel-injected engines allows the vehicle’s ECU to control the airflow at idle. Vacuum leaks are where an airflow interruption in the intake manifold area causes unmetered air to enter the engine. Usually, this issue is heard and not seen, as it causes a distinct hissing sound.

High RPM from fuel injectors

Gauge Cluster with speedometer
Gauge Cluster | Getty Images

Why Do Cars Need Spark Plugs?

The next set of issues starts with faulty spark plugs. Spark plugs are responsible for igniting the air/fuel mixture inside the cylinder. If there is a bad plug, it may cause the RPM to fluctuate. Another engine issue could be dirty fuel injectors. Even with a fuel filter, the fuel injectors may become clogged with sediment over time. The dirty injectors will decrease performance and cause the RPM to struggle. Lastly, there could be an issue with the transmission. A leak in the transmission could cause the torque converter inside an automatic transmission to slip, making the RPM jump. As a result, the transmission will wear even faster as the fluid is not protecting the internals. A lurching, RPM jumping feel when you press on the gas is the best indication of this problem.

Should you pay more attention to RPM?

In short, absolutely pay attention to your RPM. Not only will it help you take care of the engine by not revving it too high, but it will also let you know if there is an issue. From the list of issues above, there may be something to look for next time you go for a drive. If you find a problem, it may be best to take it to a shop for diagnosis.